It's the 9th inning of the bull market - and there's no chance of extra innings, David Rosenberg warns

Wall Street may be embracing the Nasdaq's return to all-time highs, but Gluskin Sheff's David Rosenberg isn't ready to abandon his bear case for stocks - he's strengthening it.

"What I'm seeing is the makings of a double top in the stock market," the firm's chief economist and strategist said Monday on CNBC's "Trading Nation." "We are in basically the ninth inning right now, and it's not going into extra innings. So I say, you don't play the momentum."

During an appearance on CNBC in June, Rosenberg was concerned investors were taking on a lot more risk than they knew by pouring money into U.S. equities. Fast forward to Feb. 5, when the Dow saw its deepest one-day point plunge ever.

Rosenberg believes more pain is coming.

"The markets are not telling you that we're in a new bull phase. They're telling you that we've gone back close to the high end of the range," he said. "My sense is that we're going to roll off the high end of the range, and go back and retest the low end of the range."

He lists several factors supporting another leg lower. They include climbing trade tensions sparked by President Donald Trump's aluminum and steel tariffs, a more hawkish Federal Reserve, a ballooning budget deficit and frothy stock market valuations.

Among the first Wall Street strategists to turn bullish following the 2008 financial crisis, Rosenberg is drawing parallels between that period and the current one. He says with each new high, investors are hearing the same thing: Follow the momentum.

"These people that are telling you to play momentum and to throw valuations in the dustbin? I got to tell you, I've been in this business for 30 years, I hear that close to every market top. You want to do the exact opposite right now, and you don't want to be the pig that gets slaughtered," Rosenberg said. "This is the ideal time when the markets rally to take some profits off the table."

According to Rosenberg, the signals are flashing late cycle. So, it'll pay for investors to act more cautious.

For investors who don't want to move entirely to cash, he recommends areas of the market that have been laggards.

"I'd be more prone to getting out of these very whippy and flashy growth stocks and moving more towards value," he said.

Rosenberg also likes Japan - which he has called the "most under-owned stock market on the planet."

"I've made a whole career out of not following the herd," Rosenberg said. "I think that it's basically just playing it safe."